This invention relates generally to a rodent cage which may be used as a static unit or in connection with a ventilated cage and rack system and, in particular, to a rodent cage that may be used for a variety of rodent types including but not limited to rats, mice, gerbils, hamsters and guinea pigs.
Ventilated cage and rack systems are well known in the art. One such ventilated cage and rack system is disclosed in U.S. Pat. No. 4,989,545, assigned to Lab Products, Inc., in which an open rack system including a plurality of shelves, each formed as an air plenum is provided. A ventilation system is connected to the rack system for ventilating each cage in the rack.
In prior art ventilated cage and rack systems, cages of different sizes are used to accommodate rodents of different types. These sizes are selected according to Institute Laboratory Animal Resources (ILAR) guidelines which set non-binding minimums for the size and dimension of cages for particular rodents. For example, for mice that weigh more than 25 grams, a cage having a dimension of at least 15 square inches per mouse is required. Similarly, rats up to 400 grams in size require a cage of at least 40 square inches per rat. Similar requirements are mandated for hamsters and guinea pigs by the Animal Welfare Act (AWA).
A drawback of the prior art cages is that a variety of different cage sizes, necessary to support the different rodent types, must be inventoried and managed so that the appropriate cage size is available for a particular study. This problem is exacerbated in large research facilities, for example, the National Institute of Health (NIH), where 20 to 30 different cage sizes have to be coordinated. Furthermore, each different cage size requires that the corresponding rack that supports the particular cage size and corresponding accessories be used. This forces the facility to inventory and manage a variety of different rack sizes as well. Accordingly, it would be desirable to provide a single cage size which is suitable for different rodent types thereby simplifying the maintenance of cage and rack systems.
The prior art cages include a cage bottom having four walls and a base with an open top. A wire bar lid, that stretches across the top of the cage bottom and extends into the cage bottom, is disposed between the cage bottom and bonnet. A bonnet supporting an air filter thereon is placed on top of the cage bottom wire bar lid thereby covering the cage bottom. The wire bar lid is constructed from stainless steel and supports food and water in the cage while also preventing the rodents, particularly rats, from gnawing through the bonnet and damaging the filter or escaping from the cage.
Several problems exist with the use of the wire bar lid in the prior art cage design. First, because the wire bar lid extends into the cage bottom, it creates an artificial ceiling between the cage bottom and the bonnet thereby reducing the amount of area and height available for the rodents. Also the wire bar lid must be removed to provide access to the animal requiring labor and work space for placing the lid during use. Also, the wire bar lid prevents the bonnet from sitting flush on the cage bottom thereby allowing air to either escape or enter the cage bottom over the lid wires creating a Venturi effect in a ventilated cage environment. Although this problem is most pronounced when rounded wire bar lids are used, it nevertheless exists even when flat rimmed wire bar lids are employed. Accordingly, it is desirable to provide a rodent cage in which a wire bar lid is not required so that the usable area for rodents is maximized and ventilation to the cage is improved.
The present invention is for a rodent cage used in various rack systems that can support a variety of rodent types. In accordance with the present invention, the rodent cage includes a cage bottom having a plurality of integral side walls, a floor and an open top end. A peripheral lip extends continuously around the top end and a pair of recesses are formed in the peripheral lip. A feeder assembly has a frame and at least one section descending therefrom. The frame has a pair of flanges extending therefrom so that when the feeder assembly is disposed in the cage bottom, the pair of flanges is received within the respective recesses. A bonnet is placed on the top of the cage bottom and is dimensioned and sized for sealing the cage bottom. A lock is disposed on the bonnet for preventing rodents in the cage from displacing the bonnet from the cage bottom.
Accordingly, it is an object of the present invention to provide a rodent cage that can be used to house different rodent types.
Another object of the present invention is to provide a rodent cage with an efficient size for a variety of rodents.
Another object of the present invention is to provide a rodent cage having more useable space while protecting a filter from damage.
Yet another object of the invention is to provide a cage which reduces the ability of rats to damage the cage by gnawing.
Still another object of the invention is to provide a simple structure for locking the bonnet to the cage bottom.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combination of elements and arrangements of parts which will be exemplified in the construction here and after set fort, the scope of the invention will be indicated in the claims.